Toptal is a marketplace for top C# developers, engineers, programmers, coders, architects, and consultants. Top companies and start-ups choose Toptal C# freelancers for their mission critical software projects.

Hire Freelance C# Developers and Engineers

Charles Cook, Ph.D.Charles has a Ph.D. in aerospace engineering and spent three years developing custom data processing and analysis programs for NASA. He specializes in scalable, enterprise-level application development and engineering solutions for exceptionally high throughputs. He is also the founder and owner of GreatVocab.com, for which he developed the core system using novel concepts in data analysis and control theory.

Charles has a Ph.D. in aerospace engineering and spent three years developing custom data processing and analysis programs for NASA. He specializes in scalable, enterprise-level application development and engineering solutions for exceptionally high throughputs. He is also the founder and owner of GreatVocab.com, for which he developed the core system using novel concepts in data analysis and control theory. Click to continue

Dmitry PavlovDmitry is a senior .NET and C# developer with over thirteen years of experience in creating web applications. He has received the Microsoft MVP (Visual C#) Award seven times since 2008 and is a capable team leader. Dmitry has also received Master of Science degrees in computer science as well as in structural geology and modeling.

Dmitry is a senior .NET and C# developer with over thirteen years of experience in creating web applications. He has received the Microsoft MVP (Visual C#) Award seven times since 2008 and is a capable team leader. Dmitry has also received Master of Science degrees in computer science as well as in structural geology and modeling. Click to continue

Richard HardebeckRichard has worked at a broad range of companies from small startups to large multinationals with often overlapping roles of software developer, quantitative analyst, and financial market professional. He is comfortable with all aspects of software development, from writing efficient algorithms and data structures, designing full system architectures, and managing and improving interfaces with legacy code.

Richard has worked at a broad range of companies from small startups to large multinationals with often overlapping roles of software developer, quantitative analyst, and financial market professional. He is comfortable with all aspects of software development, from writing efficient algorithms and data structures, designing full system architectures, and managing and improving interfaces with legacy code. Click to continue

Richard RozsaRichard Rozsa offers a vision of data as a self formatting entity. For more than 30 years, he's delivered top quality technical architecture, programming, testing and solutions for complex problems--on-time and within budget. He's extremely flexible and able to integrate as a standalone freelancer or within teams.

Richard Rozsa offers a vision of data as a self formatting entity. For more than 30 years, he's delivered top quality technical architecture, programming, testing and solutions for complex problems--on-time and within budget. He's extremely flexible and able to integrate as a standalone freelancer or within teams. Click to continue

Victor BuenoVictor is a seasoned .NET developer with over 17 years of experience focusing on the Microsoft technology stack. He develops a wide range of software, including web apps, back-end services, databases, and mobile apps. He is particularly interested in high-performance multi-threaded development.

Victor is a seasoned .NET developer with over 17 years of experience focusing on the Microsoft technology stack. He develops a wide range of software, including web apps, back-end services, databases, and mobile apps. He is particularly interested in high-performance multi-threaded development. Click to continue

John R. KosinskiAs a full-stack mobile developer, John has been developing since around 2000. Early on he did some C++, ASP, VB6, and other things but since, .NET came out most of his work has been in .NET. His work experience up until 2009 was in the NYC and NYC area; since 2009, he's been living and working in Thailand. Currently, he's consulting remotely for US clients and working on iOS, Android, and IoT projects.

As a full-stack mobile developer, John has been developing since around 2000. Early on he did some C++, ASP, VB6, and other things but since, .NET came out most of his work has been in .NET. His work experience up until 2009 was in the NYC and NYC area; since 2009, he's been living and working in Thailand. Currently, he's consulting remotely for US clients and working on iOS, Android, and IoT projects. Click to continue

Konstantin StartsevKonstantin has 9+ years of software engineering experience, including a number of great jobs working with big companies and many jobs with start-up companies and medium-sized mobile and web agencies. Over the past few years, he has been developing web solutions for the automation of business processes using C# and ASP.NET MVC or Java with Play! Framework and various front-end frameworks (e.g., jQuery, AngularJS, KnockoutJS, TypeScript, etc.).

Konstantin has 9+ years of software engineering experience, including a number of great jobs working with big companies and many jobs with start-up companies and medium-sized mobile and web agencies. Over the past few years, he has been developing web solutions for the automation of business processes using C# and ASP.NET MVC or Java with Play! Framework and various front-end frameworks (e.g., jQuery, AngularJS, KnockoutJS, TypeScript, etc.). Click to continue

Anne AdamsAfter building financial trading applications for 8 years as an engineer at Merrill Lynch, Anne has since gone on to found and build LoudUp, a music-based social network that she designed, built, and launched from the ground up. She specializes in .NET technologies and JavaScript.

After building financial trading applications for 8 years as an engineer at Merrill Lynch, Anne has since gone on to found and build LoudUp, a music-based social network that she designed, built, and launched from the ground up. She specializes in .NET technologies and JavaScript. Click to continue

Johan HernandezJohan is a mobile app and cloud back-end developer with over 15 years of experience. He's been telecommuting for startups in the USA since 2010. He has worked with enterprise stacks for a number of years, but more recently his primary focus has been on building native apps for mobile and desktop (Mac, iOS, Android and Windows) using Swift, Objective-C, Java, Kotlin, and C#. He also builds his own RESTful back-ends with Rails, Node, and Golang.

Johan is a mobile app and cloud back-end developer with over 15 years of experience. He's been telecommuting for startups in the USA since 2010. He has worked with enterprise stacks for a number of years, but more recently his primary focus has been on building native apps for mobile and desktop (Mac, iOS, Android and Windows) using Swift, Objective-C, Java, Kotlin, and C#. He also builds his own RESTful back-ends with Rails, Node, and Golang. Click to continue

C# came in as a new kid on the block. At first it was ignored, then it was ridiculed, and then it was fought against, but now it continues to win over developers all over the world. The direct result of this growth is a large number of developers that are using C#. This guide covers topics that every C# developer needs to have mastered, and is essential when making your next hire.

“Toptal allows corporations to quickly assemble teams that have the right skills for specific projects.”

Steven Norton

Testimonials

“I’m a big believer in the saying, ‘hire smart, or manage tough’. For us non-hackers, Toptal takes the guesswork out of hiring. Their coders are vetted, and the work is guaranteed. Why look anywhere else?”

Greg Archbald

Founder & CEO @ Greasebook

“Toptal understood our project needs immediately. We were matched with an exceptional freelancer from Argentina who, from Day 1, immersed himself in our industry, blended seamlessly with our team, understood our vision, and produced top-notch results. Toptal makes connecting with superior developers and programmers very easy.”

Jason Kulik

Co-Founder @ ProHatch

“Working with Toptal has been a great experience. Prior to using them, I had spent quite some time interviewing other freelancers and wasn't finding what I needed. After engaging with Toptal, they matched me up with the perfect developer in a matter of days. The developer I'm working with not only delivers quality code, but he also makes suggestions on things that I hadn't thought of. It's clear to me that Amaury knows what he is doing. Highly recommended!”

George Cheng

CEO @ Bulavard, Inc.

“In Higgle's early days, we needed the best-in-class developers, at affordable rates, in a timely fashion. Toptal delivered! ”

Lara Aldag

CEO @ Higgle

“Chris is an absolutely exceptional Python developer, and the single most efficient programmer I've ever worked with. From the beginning of the project, Chris was instantly a vital member of the team. He's proactive, self-managed, knowledgeable, and efficient. I point him in a direction, and he delivers. Chris will be a part of the Crisis Cleanup team as long as I have anything to say about it.”

Aaron Titus

Project Manager @ Crisis Cleanup

“We're a small firm with big dreams. After trying 4 or 5 local or outsourced developers, we were out of options. I'd heard of Toptal, but was worried that my company wasn't big enough for them. After calling them up, I found out that I didn't need to meet any minimum budget and was immediately put in touch with a developer to talk through my problems and goals. A day later, he got back to me with a list of possible solutions. After 9 months and 5 developers, Toptal got me my solution in a single week at a price I could afford.”

Kevin Ramirez

Co-Founder @ SixtyVocab.com

“We used Toptal to hire a developer with extensive Amazon Web Services experience. We interviewed four candidates, one of which turned out to be a great fit for our requirements. The process was quick and effective. ”

Abner Guzmán Rivera

CTO and Chief Scientist @ Photo Kharma

“Toptal makes finding qualified engineers a breeze. We needed an experienced ASP.NET MVC architect to guide the development of our start-up app, and Toptal had three great candidates for us in less than a week. After making our selection, the engineer was online immediately and hit the ground running. It was so much faster and easier than having to discover and vet candidates ourselves.”

Jeff Kelly

Co-Founder @ Concerted Solutions

“I am more than pleased with our experience with Toptal. The professional I got to work with was on the phone with me within a couple of hours. I knew after discussing my project with him that he was the candidate I wanted. I hired him immediately and he wasted no time in getting to my project, even going the extra mile by adding some great design elements that enhanced our overall look.
”

Paul Fenley

Director @ K Dunn & Associates

“Toptal has helped my business tremendously by finding, vetting, and recruiting the talent I need, at the right time. I’d definitely recommend it to others.”

Xavier Xicay

CEO & Creative Director @ Tuatara Corp

“I'm incredibly impressed with the caliber of the Toptal developers I have worked with - they have proven themselves to be both dedicated and highly talented. We will most definitely continue to work with Toptal.
”

Savannah de Savary

Founder @ Industry Hub

“As an internet marketing company specializing in pay-per-click management, our clients frequently ask us to provide services that fall outside the scope of our primary business. We have found Toptal to be exactly the resource we need to connect with contractors so we can deliver our clients top tier web development talent at a reasonable cost.”

Pashmina Lalchandani

Owner @ Flowsimple

“What attracted us to Toptal was that Toptal is sourcing its talent from a global pool. The selection process is very stringent. They’re sourcing the talent not only based on capabilities -- sourcing the best 3% -- but also based on cultural fit, which is really important to us. We had an amazing experience working with Toptal. Toptal helped us achieve our goals by bringing us very high-quality resources, on very short notice.”

Elmar Platzer

Digital Transformation Leader, CSR Australia @ CSR Limited

“My experience with Toptal has exceeded expectations. I needed to quickly find a front-end developer, and the first person they recommended was a perfect fit. A month later, I needed an iOS developer and they delivered again. I'm incredibly impressed with the quality of the people in Toptal's network and how quickly I was able to find a match for my needs.”

Toptal is a marketplace for top C# developers, engineers, programmers, coders, architects, and consultants. Top companies and start-ups choose Toptal freelancers for their mission-critical software projects.

Charles has a Ph.D. in aerospace engineering and spent three years developing custom data processing and analysis programs for NASA. He specializes in scalable, enterprise-level application development and engineering solutions for exceptionally high throughputs. He is also the founder and owner of GreatVocab.com, for which he developed the core system using novel concepts in data analysis and control theory.

Dmitry is a senior .NET and C# developer with over thirteen years of experience in creating web applications. He has received the Microsoft MVP (Visual C#) Award seven times since 2008 and is a capable team leader. Dmitry has also received Master of Science degrees in computer science as well as in structural geology and modeling.

Richard has worked at a broad range of companies from small startups to large multinationals with often overlapping roles of software developer, quantitative analyst, and financial market professional. He is comfortable with all aspects of software development, from writing efficient algorithms and data structures, designing full system architectures, and managing and improving interfaces with legacy code.

Richard Rozsa offers a vision of data as a self formatting entity. For more than 30 years, he's delivered top quality technical architecture, programming, testing and solutions for complex problems--on-time and within budget. He's extremely flexible and able to integrate as a standalone freelancer or within teams.

Victor is a seasoned .NET developer with over 17 years of experience focusing on the Microsoft technology stack. He develops a wide range of software, including web apps, back-end services, databases, and mobile apps. He is particularly interested in high-performance multi-threaded development.

As a full-stack mobile developer, John has been developing since around 2000. Early on he did some C++, ASP, VB6, and other things but since, .NET came out most of his work has been in .NET. His work experience up until 2009 was in the NYC and NYC area; since 2009, he's been living and working in Thailand. Currently, he's consulting remotely for US clients and working on iOS, Android, and IoT projects.

Konstantin has 9+ years of software engineering experience, including a number of great jobs working with big companies and many jobs with start-up companies and medium-sized mobile and web agencies. Over the past few years, he has been developing web solutions for the automation of business processes using C# and ASP.NET MVC or Java with Play! Framework and various front-end frameworks (e.g., jQuery, AngularJS, KnockoutJS, TypeScript, etc.).

After building financial trading applications for 8 years as an engineer at Merrill Lynch, Anne has since gone on to found and build LoudUp, a music-based social network that she designed, built, and launched from the ground up. She specializes in .NET technologies and JavaScript.

Johan is a mobile app and cloud back-end developer with over 15 years of experience. He's been telecommuting for startups in the USA since 2010. He has worked with enterprise stacks for a number of years, but more recently his primary focus has been on building native apps for mobile and desktop (Mac, iOS, Android and Windows) using Swift, Objective-C, Java, Kotlin, and C#. He also builds his own RESTful back-ends with Rails, Node, and Golang.

The Vital Guide to C# Interviewing

Remember the Y2K bug? Apparently, the world was supposed to end due to havoc in computer networks all over the planet. Just one year before that, we heard announcements that 1999 will mark the end of the world because it had an inverted 666 in its name. In such turbulent times, when many were piling food in their basements, hoping that Armageddon would not find them, there were a few visionaries that were still inventing some cool stuff. One of them is Anders Hejlsberg, who gathered a team of Microsoft developers and created Cool, which was the first version of new C-like Object Oriented Language, later to be named C#.

14 years and 5 versions later, C# is one of the most popular languages in the industry. Despite the fact that James Gosling and Bill Joy stated that C# was just an imitation of Java, while some other critics even called C# a boring repetition that lacks innovation, C# is now standing tall next to all the other platforms used by millions of developers all over the world.

C# is a multi-paradigm programming language encompassing strong typing, as well as imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines. You can use it to build any type of application, whether it is a service, console, desktop, web or even smartphone application.

Each application type requires a specific set of skills on top of standard C# syntax, and finding a great C# developer is not an easy task. If you are looking for a web developer you should expect knowledge of the HTTP protocol, Web Forms, MVC Framework and Razor View Engine, while some other application will have its own challenges.

This article should help you identify a developer that understands C# in its core. Regardless on the application type, techniques and tips mentioned below should be universal to all C# developers and they should all be able to demonstrate extensive understanding of these topics.

I’ll try to cover general topics that every developer must be aware of. The purpose of this article is to point to several specific topics. Evaluating knowledge of each of them in depth would require much more than one or two questions.

Generics

Generics were one of the earliest features of the C# language. Generics make it possible to design classes and methods that defer the specification of one or more types until the class or method is declared and instantiated by client code.

Q: Consider the following code, which is part of a console application:

Optimize the code in a way to replace DeveloperList and IntegerList with one class named GenericList that will contain single doSomething method. Make sure to handle the case when GenericList is instantiated by an unexpected type.

LINQ

LINQ (Language-Integrated Query) is one of the coolest features in C#. It was introduced in Visual Studio 2008 and it provides extremely powerful query capabilities to C#. LINQ introduces standard patterns for querying and updating data supporting any kind of data store.

Even though this is a technically correct solution, it would be less desirable due to the complexity of the code.

Lambda Expressions

Lambda expressions are methods that do not require declaration. These are function that are implemented “in-line” with the rest of the code. Lambda expressions are particularly helpful for writing LINQ query expressions.

To create a lambda expression, you specify input parameters (if any) on the left side of the lambda operator =>, and you put the expression or statement block on the other side. For example, the lambda expression x => x * x specifies a parameter named x and returns the value of x squared.

The general definition of lambda expression is:

(parameters) => Code

Q: Complete the following code by implementing the methods Square and Double based on the Calculate delegate and lambda expressions.

The only thing you needed to do is add an argument name when passing in the values.

Optional Parameters

The definition of a method, constructor, indexer, or delegate can specify that its parameters are required or that they are optional. Any call must provide arguments for all required parameters, but can omit arguments for optional parameters.

Each optional parameter has a default value as part of its definition. If no argument is sent for that parameter, the default value is used.
Optional parameters are defined at the end of the parameter list, after any required parameters. If the caller provides an argument for any one of a succession of optional parameters, it must provide arguments for all preceding optional parameters. Comma-separated gaps in the argument list are not supported.

Q: Extend the Developer class with a boolean property named Enabled and a constructor that will accept name and the optional enabled value.

Asynchronous Processing

Asynchrony is essential for activities that are potentially blocking, such as when your application accesses network resources. Access to a network resource sometimes is slow or delayed. If such an activity is blocking a synchronous process, the entire application must wait. In an asynchronous process, the application can continue with other work that doesn’t depend on the network resource until the potentially blocking task finishes.

Visual Studio 2012 introduced a simplified approach, async programming, that leverages asynchronous support in the .NET Framework 4.5 and the Windows Runtime. The compiler does the difficult work that the developer used to do, and your application retains a logical structure that resembles synchronous code. As a result, you get all the advantages of asynchronous programming with a fraction of the effort.

The async and await keywords in C# are the heart of async programming. By using those two keywords, you can use resources in the .NET Framework or the Windows Runtime to create an asynchronous method almost as easily as you create a synchronous method. Asynchronous methods that you define by using async and await are referred to as async methods.

After five seconds of the application being paused, the output of this code would be:

Delayed
Final: Delayed
Awaited

Note: The first “Delayed” will show up after a delay of one second.

The reason for this is in the way async methods are handled in C#, and the difference between Task.Delay and Thread.Sleep. The SayAwaited method will execute like any other method until it reaches the await command. At this point, C# will start another thread for executing Task.Delay on the new thread, while releasing current thread to proceed with next action, which is SayDelayed. After putting the main thread to sleep for one second, SayDelayed will set the value for the statement and execution will proceed with the remaining commands, WriteLine and ReadLine. While this is all happening, SayAwaited will be nicely paused in its own thread, and after 5 seconds it will set statement to “Awaited”, produce its own output, and return.

Q: Would there be any difference if statement = "Awaited" would be execute before await command? Explain your answer.

The reason for this is that the “Awaited” value is assigned to statement before the await command is called. By the time Console.WriteLine(statement); in SayAwaited is executed, the value of statement has already been updated by the SayDelayed method.

Stay Sharp!

C# came in as a new kid on the block. At first it was ignored, then it was ridiculed, then it was fought against. Now it continues to win over developers all over the world. The direct result of this growth is the large number of developers that are using C#.

This article referenced topics that every C# developer should master. Make sure to cover these topic when you are looking for a great C# developer, and you will be one step closer to identifying the best of the best.